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EFHW Portable Antenna
Homer_2WR183
End Fed Portable Antenna

This describes the pictured EFHW (End Fed Half Wave) antenna in the photos below. The SWR achieved with this device was very low, 1.0:1 on the 11 meters band it was built for. Different setup locations can produce different results. I believe it could be used to tune for other bands as well. I used it as a portable, but it is in static base use now.

i1205.photobucket.com/albums/bb426/Chal_Cirilo/End%20Fed%20Portable/f0519.jpg

i1205.photobucket.com/albums/bb426/Chal_Cirilo/End%20Fed%20Portable/f0520.jpg

i1205.photobucket.com/albums/bb426/Chal_Cirilo/End%20Fed%20Portable/f0521.jpg


If interested, how to make the coil in the above photo.

Materials:
wire
wax paper
blue swimming pool flex hose
Hot glue.


1. Cut a section of this hose, cut it into strips.
2. Wax paper rolled and taped onto cylinder such as PVC pipe.
3. Hot glue strips of hose onto wax paper.
4. Wrap wire for coil around the form into the grooves.
5. Hot glue across all the blue hose strips.
6. Slide wax paper off of the PVC form, remove wax paper from within the coil.


i1205.photobucket.com/albums/bb426/Chal_Cirilo/End%20Fed%20Portable/bluehose.jpg

The capacitor is:

1.
three 3/4" x 1/8" x 3-1/2" long flat aluminum stock plates with
2. two strips of double sticky tape that has only
3. one side of the tape peeled away so it can stick to the bar it is on.

a. The coil and the cap are wire together parallel (each end wired together).
b. At one end the ground side (braid) of the coax is attached, and at the other end the antenna wire is attached.
c. The center conductor of the coax is fitted with a jumper and alligator clip so as to be used to tap the coil.
d. The coax attaches via a PL239 fitted to the backing.
e. Everything is mounted on a nonconducting backing. I have put some in a plastic pencil box, or a Tupperware box.


To tune.
1. Measure out the wire antenna for the band you want to work (the one in the photo work the world on 11 meters for a friend in Ft Worth, Texas as a stealth antenna in an HOA neighborhood)and attach it to the antenna as in the photos - the opposite end from the PL239 connection.

2. Clip the coil midway from each end with the alligator clip jumper wire.

3. Begin to adjust the sliding bars of the capacitor plates until you achieve the lowest possble match. Any means of temporarily holding them together can be utilized as long as it is non-conducting. I have used plastic potatoe chip bag clips, and wooden spring loaded clothes pins.

4. When the tune is as low as you can get it with the capacitor adjustment retap the coil at another spot until the tune comes down again.

Hopefully you are done by now, but if not continue to go back and forth with the cap/coil adjustments process until the job is done.


This capacitor can be built with only two cap plates, but three should give more control over a wider range of frequencies/bands.

In the photo can be see how the cap plates were hot glued to remain static for center frequency on US CB 11 meters band.
Edited by Homer_2WR183 on 03-01-2013 20:10
________________________________

i1205.photobucket.com/albums/bb426/Chal_Cirilo/avatar/avatar04_zps1c27fe08.png
My friends call me Homer
 
Homer_2WR183
Thanks, Paul.
I did have fun with it.
Then a friend came by who I thought could use it.
________________________________

i1205.photobucket.com/albums/bb426/Chal_Cirilo/avatar/avatar04_zps1c27fe08.png
My friends call me Homer
 
Homer_2WR183
This is an example of one I made in a plastic school supply box that I use since gifting the one above:

i1205.photobucket.com/albums/bb426/Chal_Cirilo/halfmatch/match1_zps334606e4.jpg

i1205.photobucket.com/albums/bb426/Chal_Cirilo/halfmatch/match2_zps621e05d8.jpg
________________________________

i1205.photobucket.com/albums/bb426/Chal_Cirilo/avatar/avatar04_zps1c27fe08.png
My friends call me Homer
 
19LV001
Love this projects thanks for sharing, and you slogan It's not grazy, if it works lol... happy building
 
www.limavictordx.com
Homer_2WR183
Glad you enjoyed it.
________________________________

i1205.photobucket.com/albums/bb426/Chal_Cirilo/avatar/avatar04_zps1c27fe08.png
My friends call me Homer
 
19LV002 PJ
Nice idea love it, mabey i will make my self one for the porto!
thanks for sharing!

keep up the good work!!

73'

PJ
 
www.limavictordx.com
Homer_2WR183
It's easy to do. Takes about an hour, but well worth it.
These are useful for a permanent base antenna, too.

i1205.photobucket.com/albums/bb426/Chal_Cirilo/bottom%20fed%20halfwave/6412/P0013a.jpg

i1205.photobucket.com/albums/bb426/Chal_Cirilo/bottom%20fed%20halfwave/6612/p0013.jpg
________________________________

i1205.photobucket.com/albums/bb426/Chal_Cirilo/avatar/avatar04_zps1c27fe08.png
My friends call me Homer
 
19LV002 PJ
will try it for shure and will upload here on the cluster!
 
www.limavictordx.com
Homer_2WR183
I'll be looking for it.
________________________________

i1205.photobucket.com/albums/bb426/Chal_Cirilo/avatar/avatar04_zps1c27fe08.png
My friends call me Homer
 
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